Inflammation is the complex biological response of vascular tissues to pathogens, damaged cells, chemical signals or irritants Inflammation may be thought of as an attempt by an organism to remove injurious stimuli and initiate tissue healing. Inflammation can be classified as either acute or chronic.
Acute inflammation is a short-term process characterized by swelling, redness, pain, heat, and loss of function caused by the increased movement of plasma and leukocytes from the blood into the injured tissues. Acute inflammation is initiated by the blood vessels adjacent to the injured tissue, which adapt to allow the exudation of plasma proteins and leukocytes into the surrounding tissue. The increased flow of fluid into the tissue causes the characteristic swelling associated with inflammation, and the increased blood flow to the area causes the reddened color and increased heat. The blood vessels are also altered to permit the extravasation of leukocytes through the endothelium and basement membrane constituting the blood vessel. Once in the tissue, the cells migrate along a chemotactic gradient to reach the site of injury, where they can attempt to remove the stimulus and repair the tissue. Several biochemical cascade systems, consisting of chemicals known as plasma-derived inflammatory mediators, act in parallel to propagate and mature the inflammatory response. These include the complement system, coagulation system and fibrinolysis system. Removal of the injurious stimuli causes down-regulation of the inflammatory response and concludes acute inflammation. Down regulation halts the recruitment of monocytes into the inflamed tissue, existing macrophages exit the tissue via lymphatics and wound healing begins. The causes of acute inflammation include
Burns
Chemical irritants
Frostbite
Toxins
Infection by pathogens
Necrosis
Physical injury (blunt or penetrating)
Immune reactions due to hypersensitivity
Ionizing radiation
Foreign bodies, including splinters and dirt
The inflammatory response must be actively terminated to prevent unnecessary “bystander” damage to tissues, failure to do so results in prolonged inflammation and cellular destruction.
Prolonged inflammation, known as chronic inflammation, leads to a progressive shift in the type of cells which are present at the site of inflammation.
In chronically inflamed tissue the stimulus is persistent. As a result, recruitment of monocytes is maintained, existing macrophages are anchored in place, and macrophages proliferation is stimulated. Macrophage cells are powerful defensive agents but they release toxins including reactive oxygen species that are injurious to the organism's own tissues, leading to tissue destruction. Chronic inflammation can be caused by persistent acute inflammation, bacterial infection, prolonged exposure to a chemical agent, or automimmune reactions to name a few causes.
Abnormalities associated with inflammation comprise a large, unrelated group of disorders which underlay a variety of human diseases including allergic reactions and some myopathies, cancer, atherosclerosis, ischemic heart disease, asthma, autoimmune diseases, chronic inflammation, chronic prostatitis, glomerulonephritis, hypersensitivities, inflammatory bowel diseases, pelvic inflammatory disease, reperfusion injury, rheumatoid arthritis, transplant rejection.